Emergy evaluation and economic analysis of three wetland fish farming systems in Nansi Lake area,China

Emergy and economic methods were used to evaluate and compare three fish production models, i.e., cage fish farming system, pond intensive fish rearing system and semi-natural extensive pond fish rearing system, in Nansi Lake area in China in the year 2007. The goal of this study was to understand the benefits and driving forces of selected fish production models from ecological and economic points of view. The study considered input structure, production efficiency, environmental impacts, economic viability and sustainability. Results show that the main difference among the three production systems was the emergy cost for fish feed associated with their feeding system, i.e., feeding on natural biomass such as plankton and grass or on commercial feedstock. As indicated by EYR, ELR and ESI, it can be clearly shown that the intensive production model with commercial feed is not a sustainable pattern. However, the point is that more environmentally sound patterns do not seem able to provide a competitive net profit in the short run. The intensive pond fish farming system had a net profit of 2.57E+03 $/ha, much higher than 1.27E+03 $/ha for cage fish farming system and slightly higher than 2.37E+03 $/ha for semi-natural fish farming system. With regard to the drivers of local farmer’s decisions, the accessibility of land for the required use and investment ability determine the farmer’s choice of the production model and the scale of operation, while other factors seem to have little effect. Theoretically, the development of environmentally sustainable production patterns, namely water and land conservation measures, greener feed as well as low waste systems is urgently needed, to keep production activities within the carrying capacity of ecosystems. Coupled emergy and economic analyses can provide better insight into the environmental and economic benefits of fish production systems and help solve the problems encountered during policy making.     

Issues,impacts, and implications of shrimp aquaculture in Thailand

Water quality impacts to and from intensive shrimp aquaculture in Thailand are substantial. Besides the surface and subsurface salinization of freshwaters, loadings of solids, oxygen-consuming organic matter, and nutrients to receiving waters are considerable when the cumulative impacts from water exchange during the growout cycle, pond drainage during harvesting, and illegal pond sediment disposal are taken into account. Although just beginning to be considered in Thailand, partial recirculating and integrated intensive farming systems are producing promising, if somewhat limited, results. By providing on-site treatment of the effluent from the shrimp growout ponds, there is less reliance on using outside water supplies, believed to be the source of the contamination.The explosion in the number of intensively operated shrimp farms has not only impacted the coastal zone of Thailand, but has also resulted in an unsustainable aquaculture industry. Abandonment of shrimp ponds due to either drastic, disease-caused collapses or more grandual, year-to-year reductions in the productivity of the pond is common. To move Thailand towards a more sustainable aquaculture industry and coastal zone environment, integrated aquaculture management is needed. Components of integrated aquaculture management are technical and institutional. The technical components involve deployment of wastewater treatment and minimal water-use systems aimed at making aquaculture operations more hydraulically closed. Before this is possible, technical and economic feasibility studies on enhanced nitrification systems and organic solids removal by oxidation between production cycles and/or the utilization of plastic pond liners need to be conducted. The integration of semi-intensive aquaculture within mangrove areas also should be investigated since mangrove losses attributable to shrimp aquaculture are estimated to be between 16 and 32% of the total mangrove area destroyed betweeen 1979 and 1993.Government policy needs to devote as much attention to sustainability issues as it has on promoting intensive pond culture. Such a balanced policy would include training and education monitoring and enforcement, rehabilitating abandoned ponds, managing land use within the coastal zone, more community involvement, and government reorganization to eliminate overlapping jurisdictions among agencies.As integrated aquaculture management becomes more the practice than the exception, less risk of crop failure to the industry and reduced discharge loadings from intensively managed shrimp ponds to receiving waters can be expected. Projected limitations on growing and marketing shrimp in the future, such as scarcity of land and broodstock, continued disease outbreaks, negative publicity, regulatory enforcement, water treatment and solids disposal costs, and increased competition from growers in other Asian countries will also drive the government and the industry towards adopting integrated aquaculture management.The data for this paper was obtained while the senior author was a Visiting Fulbright Researcher at the Coastal Resources Institute (CORIN), Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand.     

Large-scale shrimp farming in coastal wetlands of Venezuela,South America: Causes and consequences of land-use conflicts

In Venezuela, large-scale shrimp farming began in the 1980s. By 1987, the Ministry of Environment and Natural Resources (MARNR) had received 14 proposals for approval. A developer illegally started the construction of ponds at the Píritu Lagoon in the State of Anzoátegui before the authorization process was completed. This action triggered a land-use conflict. This study identifies the causes for public protest and determines the consequences of this conflict for land-use management. The results show that public protest was based on the impacts of the partial construction of ponds. These impacts were related to direct removal of wetlands, interruption of natural patterns of surface flows, and alteration of feeding grounds of some bird species with migratory status. Consequences were identified in relation to the role that nongovernmental organizations (NGOs) play in land-use conflicts and the actions that MARNR could take in the future to prevent and solve similar situations.     

Solid waste management in urban areas: Development and application of a decision support system

A decision support system (DSS) developed to assist the planner in decisions concerning the overall management of solid waste at a municipal scale is described. The DSS allows to plan the optimal number of landfills and treatment plants, and to determine the optimal quantities and the characteristics of the refuse that has to be sent to treatment plants, to landfills and to recycling. The application of the DSS is based on the solution of a constrained non-linear optimization problem. Various classes of constraints have been introduced in the problem formulation, taking into account the regulations about the minimum requirements for recycling, incineration process requirements, sanitary landfill conservation, and mass balance. The cost function to be minimized includes recycling, transportation and maintenance costs. The DSS has been tested on the municipality of Genova, Italy, and the results obtained are presented.